Sunday, 25 August 2013

Scientific errors in Christadelphian attacks on evolution: The Testimony magazine - 3

The July 2011 edition of The Testimony contains an article which claims that:

 The structure of the tail of the whale and of the dolphin is unique. There is no simple way for it to have developed from another animal. It thus provides further evidence of design by the Creator.

Any article which begins with an argument from incredulity is not off to a good start. When it makes demonstrably false such as “ Whales, like all mammals, appear suddenly in the fossil order, with no sign of transitional species from which they might have evolved.”, then one can completely dismiss the article as yet another collection of special creationist misunderstanding and distortion. The final icing on the cake is the fact that it cites as evidence the long-discredited book “The Neck of the Giraffe”. The fact that such an error-ridden article made it into the Testimony reflects poorly on its science editor, David Burges, and provides more evidence of how the Testimony’s anti-evolution stance harms its credibility.

The claim that whales “appear suddenly in the fossil order, with no sign of transitional species from which they might have evolved” <2> is incorrect. Since the early 1980s, numerous cetacean transitional fossils have been discovered, detailing the macroevolutionary change from the earliest cetaceans such as Pakicetus <3> through to Ambulocetus <4> , the remingtonocetids such as Remingtonocetus <5> and Kutchicetus <6>, the protocetids such as Rodhocetus <7>, Artiocetus <8> and Georgiacetus <9> through to the first fully aquatic cetaceans such as Basilosaurus <10>. Furthermore, the origin of mysticetes has been clarified by the discovery of transitional fossils such as Aetiocetus weltoni <11> which possessed both teeth and palatal nutrient foramina that are associated with baleen. As J.G.M. Thewissen, one of the leading researchers in cetacean evolution noted, “cetacean origin is one of the best known examples of macroevolution documented in the fossil record.” <12> Whale evolution is one of the best documented examples of macroevolutionary change in the fossil record, and any claim that no whale transition fossils exist is simply incorrect.

The Evolution of Whales (Source:

Even more disturbing was the citation of Francis Hitching’s poorly regarded <13> book “The Neck of the Giraffe” as a source for the assertion that whale evolution poses a problem for evolutionary biology. Apart from the fact that Hitching was not a scientist but a television script writer who uncritically sourced material from special creationists, his book was written in 1982, nearly thirty years ago, making it utterly dated. Furthermore, many whale transitional fossils have been discovered since Hitching’s book was published, while the revolution in molecular biology and genomics has produced another line of evidence supporting whale evolution. Evolutionary biologists as mentioned above correctly regard whale evolution as one of the premier examples of large scale evolutionary change, and anyone arguing otherwise is advocating a position flatly at variance with the evidence. At the very least, citation of the primary literature to support that position is needed, rather than a dated secondary source from a non-expert. 

On the subject of the evolution of cetacean locomotion, even a cursory examination of the primary literature would disabuse anyone of the belief that this is an intractable problem for evolution. The evolutionary biologist Frank Fish <14>`proposed a model for cetacean locomotor evolution that postulated a swimming mode similar to that of otters. The discovery of Ambulocetus, which has limbs proportionally similar to that of otters <15> has made this prediction quite likely. Thewissen notes:
Like modern cetaceans it swam by moving its spine up and down, but like seals, the main propulsive surface was provided by its feet. As such, Ambulocetus represents a critical intermediate between land mammals and marine cetaceans. <16>
With respect to the later cetacean Rodhocetus, Gingerich et al observe:
Rodhocetus has high neural spines on anterior thoracics and a pelvis that articulates directly with a sacrum, features of mammals that support their weight on the land. However, it had short cervicals to make the anterior body more rigid, large unfused sacrals and a reduced femur, characteristic of later archaeocetes. In other words, its morphology is transitional between terrestrial and aquatic forms. <17> (Emphasis mine)

Skeletons and Body Forms of Modern Whales and Fossil Ancestors

The reconstructed skeletons (black) from modern whales (top) and various ancestral skeletal forms (series below) are in chronological order (from Pakicetus up). Indohyus is an extinct whale “cousin”. Relative body size, to scale, is indicated by the gray shapes at the right of each animal. (Source: BioLogos - Evidences for Evolution, part 2b: The Whale's Tale)

The available evidence suggests that cetacean locomotor evolution proceeded <18> along the following path:

  • Quadrupedal Paddling
  • Alternating Pelvic Paddling
  • Simultaneous Pelvic Paddling
  • Dorsoventral Undulation
  • Caudal Oscillation
There is always likely to be further refining of these models as further palaeontological evidence emerges, but the skeleton of Ambulocetus strongly suggests that it undulated its hind limbs and tail dorsoventrally. Likewise, Rodhocetus is clearly transitional between aquatic and terrestrial modes of life as demonstrated by its combination of primitive and derived features. The evolution of cetacean locomotion is anything other than an intractable problem for modern evolutionary biology.
The changing cetacean body plan during the first ten million years of cetacean evolution. Pictured are five families of archaeocetes, the oldest being the pakicetids, while the youngest are the basilosaurids (modified from Thewissen et al. (2002), © Annual Reviews (Source: Evolution: Education and Outreach
Volume 2Issue 2pp 272-288), 

Fossil evidence strongly suggests that whales evolved from artiodactyls, and the evidence from molecular biology confirms this. Gatesy et al <19> have demonstrated that the molecular data from milk casein genes show that hippopotami and cetaceans are sister groups, sharing a common ancestor, which is corroborated by cytochrome b data which likewise show <20> whales and hippopotami are sister taxa, as well as the molecular data from γ-fibrinogen. <21>
Even more compelling molecular evidence comes from the presence of shared retrotransposons – mobile genetic elements that cut and paste, or copy and paste themselves into different regions of the genome – that are exclusive to hippos and whales:
Analysis of the KM14, HIP4, HIP24, and AF loci show that hippopotamuses and cetaceans form a monophyletic group that excludes ruminants. In each case, the CHR-1 SINE was inserted into the genome of a common ancestor of these species, as confirmed by hybridization experiments with probes specific for CHR-1 and its flanking region...On closer examination, it was revealed that the CHR-1 SINE was integrated into a common ancestor of hippopotamuses and whales…(indicating a sister-group relationship between these taxa), whereas a MER unit was integrated into the genome of a common ancestor of ruminants only. (Emphasis mine). <22>
The presence of identical retrotransposons at the same place in the genomes of related species is prima facie evidence for common descent. As mentioned, these are mobile genetic elements that are copied from elsewhere and insert themselves randomly into other places in the genome. The odds of the same SINE or LINE inserting at the same place in the genomes of related species is vanishingly small, making common descent the only credible explanation for the pattern of retrotransposon distribution seen. As Nikaido et al point out:
SINES and LINEs are virtually unique and irreversible mutations...which is well documented with primate Alu (SINE) sequences. During the last 10 years, one of us (N.O.) has studied several hundred SINE loci, but he has never observed any occurrence of independent SINE insertions among species at identical genomic positions (i.e., between the same two nucleotides). Because the probability that a SINE / LINE will be lost once it has been inserted into the genome is extremely small, and the probability that the same SINE / LINE will be inserted independently into an identical region in the genomes of two different taxa is also very small, the probability that homoplasy will obscure phylogenetic relationships is, for all practical purposes, zero...Therefore, one can reconstruct phylogenetic trees with high confidence by considering multiple independent SINE / LINE insertion events that define given nodes in a tree. (Emphasis mine) <23>
The fact that this data is consistent with the data from nuclear and mitochondrial DNA makes the evolutionary origin of whales from artiodactyls all but certain. Anyone who attempts to dismiss whale evolution needs to account for a formidable amount of palaeontological and molecular data. Continued reliance on misunderstood articles from popular science journals such as New Scientist or utterly discredited books by Francis Hitching or Richard Milton does us no credit at all.
I would make note of one final piece of molecular evidence which is readily explained by evolution, but is otherwise inexplicable by special creation. Baleen whales have no teeth, so one would not expect to see evidence of teeth in them. However, embryonic mysticetes develop tooth buds <24>, only to resorb them later. This makes sense if mysticetes evolved from toothed whales, as the fossil evidence shows, but is pointless if they were created de novo. Likewise, one would not expect to see evidence of tooth enamel protein genes in mysticete DNA if they did not evolve from toothed ancestors. However, this is exactly what we do see:
Enamel is the hardest substance in the vertebrate body. One of the key proteins involved in enamel formation is enamelin. Most placental mammals have teeth that are capped with enamel, but there are also lineages without teeth (anteaters, pangolins, baleen whales) or with enamelless teeth (armadillos, sloths, aardvarks, pygmy and dwarf sperm whales). All toothless and enamelless mammals are descended from ancestral forms that possessed teeth with enamel. Given this ancestry, we predicted that mammalian species without teeth or with teeth that lack enamel would have copies of the gene that codes for the enamelin protein, but that the enamelin gene in these species would contain mutations that render it a nonfunctional pseudogene. To test this hypothesis, we sequenced most of the protein-coding region of the enamelin gene in all groups of placental mammals that lack teeth or have enamelless teeth. In every case, we discovered mutations in the enamelin gene that disrupt the proper reading frame that codes for the enamelin protein. Our results link evolutionary change at the molecular level to morphological change in the fossil record and also provide evidence for the enormous predictive power of Charles Darwin's theory of descent with modification. <25> (Emphasis mine)
Any argument that asserts the Creator would insert broken genes for proteins that code for tooth enamel baleen whales do not need is scarcely credible.
Whale evolution is one of the best-demonstrated examples of evolution in the fossil record, and is well-supported by powerful evidence from embryology and molecular genetics. This article not only completely fails to engage with the considerable evidence from palaeontology and molecular genetics for whale evolution, but relies uncritically on a long-debunked book by a layperson who himself relied on special creationist arguments. A competent, informed science editor would never have let an article this flawed into the magazine, and it represents yet another example of how the Testimony's anti-science agenda is destroying its credibility.
1. Edwards M “The whale tail tale” The Testimony (2011) 81:214
2. loc cit
3. Madar SI. "The postcranial skeleton of pakicetid cetaceans." J Pal. 2007;81:176–200.
4. Thewissen JGM, Madar SI, Hussain ST. "Ambulocetus natans, an Eocene cetacean (Mammalia) from Pakistan." Cour Forsch Inst Senckenberg. 1996;190:1–86.
5. Kumar K, Sahni A 1986. "Remingtonocetus harudiensis, new combination, a middle Eocene archaeocete (Mammalia, Cetacea) from western Kutch, India." Journal of Vertebrate Paleontology 6(4):326-349
6. Bajpai S, Thewissen JGM 2000. "A new, diminutive Eocene whale from Kachchh (Gujarat, India) and its implications for locomotor evolution." Current Science 79(10):1478-1489
7. Gingerich PD, Raza SM, Arif M, Anwar M, Zhou X. New whale from the Eocene of Pakistan and the origin of cetacean swimming. Nature. 1994;368:844–7.
8. Gingerich PD et al "Origin of Whales from Early Artiodactyls: Hands and Feet of Eocene Protocetidae from Pakistan" Science 2001;293:2239-2242
9. Hulbert RC Jr, Petkewich RM, Bishop GA, Burky D, Aleshire DP. "A new middle Eocene protocetid whale (Mammalia: Cetacea: Archaeoceti) and associated biota from Georgia." J Pal. 1998;72:905–25.
10. Gingerich PD, Arif M, Bhatti MA, Anwar M, Sanders WJ. "Basilosaurus drazindai and Basiloterus hussaini, new Archaeoceti (Mammalia, Cetacea) from the middle Eocene Drazinda Formation, with a revised interpretation of ages of whale-bearing strata in the Khirthar Group of the Sulaiman Range, Punjab (Pakistan)." Contr Mus Pal Univ Michigan. 1997;30:55–81.
11. Deméré T, McGowen MR, Berta A, Gatesy J. "Morphological and molecular evidence for a stepwise evolutionary transition from teeth to baleen in mysticete whales." Systematic Biology. 2008;57(1):15-37.
12. Thewissen JGM, Cooper LN, George JC, Bajpai S. "From Land to Water: the Origin of Whales, Dolphins, and Porpoises." Evo Edu Outreach 2009;2(2):272-288.
13. Feurbacher A “Francis Hitching: Commonly quoted by creationistsThe Talk.Origins Archive
14. Fish FE. "Transitions from drag-based to lift-based propulsion in mammalian swimming." Am Zool. 1996;36:628–41.
15. Thewissen JGM, Fish FE. "Locomotor evolution in the earliest cetaceans: functional model, modern analogues, and paleontological evidence." Paleobiology. 1997;23:482–90.
16. Thewissen JGM, Hussain ST, Arif M "Fossil Evidence for the Origin of Aquatic Locomotion in Archaeocete Whales" Science 2004;263:210-212
17. Gingerich PD, Raza SM, Arif M, Anwar M, Zhou X , op cit p 847
18. Thewissen Cooper LN, George JC, Bajpai S op cit. p 281
19. Gatesy J, Hayashi C, Cronin M, Arctander P. "Evidence from milk casein genes that cetaceans are close relatives of hippopotamid artiodactyls." Mol. Biol. Evol. 1996;13(7):954-63.
20. Irwin D, Arnason U "Cytochrome b gene of marine mammals: phylogeny and evolution" J Mammal. Evol. 1994 2:37-55
21. Gatesy J. More DNA support for a Cetacea/Hippopotamidae clade: the blood-clotting protein gene gamma-fibrinogen. Mol. Biol. Evol. 1997;14(5):537.
22. Nikaido M et al "Phylogenetic relationships among cetartiodactyls based on insertions of short and long interpersed elements: Hippopotamuses are the closest extant relatives of whales" Proc. Natl. Acad. Sci. USA (1999) 96:10261-10266
23. ibid, p 10264
24. Deméré T, McGowen MR, Berta A, Gatesy J op cit. p 16
25. Meredith RW, Gatesy J, Murphy WJ, Ryder OA, Springer MS (2009) "Molecular Decay of the Tooth Gene Enamelin (ENAM) Mirrors the Loss of Enamel in the Fossil Record of Placental Mammals." PLoS Genet 5(9): e1000634.